1. Field of the Invention
The present invention relates, in general, to a gamma-ray tomography scanning system and, more particularly, to a diagnostic method and system capable of applying tomography to industrial long cylindrical process systems, such as a pipeline, which are difficult to diagnose using existing medical or industrial computed tomography scanners.
2. Description of the Related Art
In general, computed tomography (CT) scanners (or computed tomographs) have been used in various fields such as industrial fields and the medical field.
CT scanners are machines that allow information about a cross-sectional view of a substance or a status of tissue, which cannot be obtained by conventional X-ray apparatuses, to be realized as an image. The CT scanner was commercialized with the invention by G. Hounsfield in 1971, and is designed to be able to observe each cross-sectional tomogram of an object to using a technique that combines images, which are obtained by penetrating X-rays into the object to be scanned at various angles, into a three-dimensional image.
One example of the conventional CT scanner is disclosed in Korean Registered Patent No. 10-0880864 (registered on Jan. 21, 2009), entitled “Nano-Scale X-ray Computed Tomography Scanner.”
In detail, the CT scanner disclosed in Korean Registered Patent No. 10-0880864 furnishes a nano-scale high-definition image using X-ray generating means having a focus size of 1 micrometer or less, in order to solve a problem, namely that although biological medical X-ray CT scanners have been used more and more with recent developments in the bio-industry and bio-engineering, they have run up against a limit because they have furnished a micro-scale definition image and thus have not been widely applied to various studies of a bio-engineering field.
Further, existing CT scanners extract a part of tissue, fix the extracted tissue to a holder, and test the extracted tissue. Since the extracted tissue is transformed into dead tissue after a predetermined time, the extracted tissue is scanned only for a short time and it is very difficult to obtain a clear image from the extracted tissue. Moreover, it is difficult for existing CT scanners to scan the tissue because of the deformation or contamination of the tissue during examination. To solve these problems, the CT scanner disclosed in Korean Registered Patent No. 10-0880864 significantly increases the test time of a biological specimen by providing cooling means to a holder fixing the specimen so as to continuously protect the specimen fixed to the holder from X-rays.
Further, another example of the conventional CT scanner is disclosed in Korean Registered Patent No. 10-0718671 (registered on May 9, 2007), entitled “X-ray Cone Beam CT Scanner Having 2-Dimensional Reference Detector and Collimator for Reference Detector.”
In detail, in order to solve a problem of existing X-ray CT scanners to which a 2-dimensional detector is applied, and in order to prevent spatial resolution from being reduced when reconstructing a 2-dimensional tomogram only when information about spatial displacement of an X-ray focus caused by irregular movement of the X-ray focus should be obtained with respect to all of X, Y, and Z axes, the CT scanner disclosed Korean Registered Patent No. 10-0718671 enhances the spatial resolution to observe a finer structure of a subject by applying a 2-dimensional detector as a reference detector instead of a one-dimensional detector, acquiring irregular movement of a X-ray tube focus over time for each view in three dimensions of X, Y, and Z axes, and reflecting the acquired information during a process of reconstructing a tomogram.
Further, another example of the conventional CT scanner is disclosed in Korean Registered Patent No. 10-0863747 (registered on Oct. 9, 2008), entitled “Apparatus for Computerized Tomography Having Pair of Synchronized Gantries.”
In detail, when X-ray tomography scanning is required to check a surgical process or the state of a lesion of a patient who is undergoing an operation, the patient should be transferred to a tomography scanning room in order to obtain a tomogram. However, various external measurement instruments, a surgical instrument, a gas and blood feeder, etc. are connected to the patient, and thus it is difficult to transfer the patient. For this reason, it is difficult to obtain the tomogram using a conventional CT scanner. Further, although the conventional CT scanner is applied to the patient undergoing an operation, the patient is located in a gantry when scanned by the CT scanner, and thus it is impossible to check the state of the patient. Moreover, the conventional CT scanner has an X-ray source and an X-ray detector mounted in one gantry, and the gantry has considerable weight. As such, it is difficult to rotate the gantry at a high speed using one driving motor. When an organ such as a heart showing continuous movement at a rapid speed is scanned, it is difficult to obtain a clear tomogram. This may cause a diagnostic error. To solve these problems, the CT scanner disclosed Korean Registered Patent No. 10-0863747 is configured to secure a space capable of treating a patient by mounting an X-ray source and an X-ray detector on a pair of gantries spaced apart from each other by a predetermined distance respectively, thereby permitting X-ray tomography scanning during an operation or treatment, and to obtain a clearer tomogram of an organ moving at a high speed by allowing each gantry to rotate at a high speed, thereby making it possible to prevent a diagnostic error.
In addition, another example of the conventional CT scanner is disclosed in Korean Registered Patent No. 10-0931304 (registered on Dec. 3, 2009), entitled “Industrial Tomography Device Using Gamma-Ray Source.”
In detail, since most existing X-ray CT scanners are intended to be used on a human body, radiation exposure and structure thereof are optimized to the human body, and thus these X-ray CT scanners are rarely used for industrial purposes. It is difficult to apply Magnetic Resonance Imagers (MRIs) to objects made of, for instance, metal. It is difficult for existing industrial X-ray CT scanners to diagnose objects having a high attenuation coefficient. Usually, industrial X-ray CT scanners are designed to rotate and scan small objects on a turntable. Consequently, since the industrial X-ray CT scanners are small CT scanners for scanning parts using the turntable, they cannot perform tomography scanning on a fixed object such as a pipe attached to facilities or a reactor.
Meanwhile, since the reactor or pipe of the industrial facilities is mostly formed of metal, it is difficult to use the X-ray CT. Even in the case of a small pipe on which X-ray CT inspection can be performed, the pipe must inevitably be separated from the facilities to perform the X-ray CT inspection. However, if to do so, there is the problem of a tremendous loss being caused by process shutdown. Due to this problem, there is a demand for a technique capable of finding out the cause of an internal abnormal phenomenon by measuring cross sections of various reactors and pipes during their operation in refineries and petrochemical industry.
However, the CT scanner of the related art has a problem in that the density and size of the object are restricted due to the use of X-rays. To solve this problem, a CT scanner using high-energy gamma rays has been developed. In this gamma-ray CT scanner, a relatively large detector is used to enhance the detection efficiency. Thus, when it compared to X-ray CT, the gamma-ray CT scanner generally obtains low resolution image from two-dimensional scanning with one-dimensional arrangement of the detector.
That is, in the case of the CT scanner that performs tomography or measurement using the one-dimensional arrangement of the detector, an apparatus designed to move up and down a subject when changing a cross section must be separately provided. This structure is restricted to large subjects.
Thus, to solve these problems, the CT scanner disclosed in Korean Registered Patent No. 10-0931394 includes: an optical system having an annular rotator into which a subject is inserted and which is allowed to be rotated left and right, a gamma-ray collimator coupled to the rotator, and a radiation detector disposed so as to face the gamma-ray collimator; and a driver installed outside the optical system so as to move up and down the optical system, whereby the restriction in size of a detectable subject and the change of a cross section of the subject is eliminated by moving up and down the optical system, and the subject is easily inspected by allowing the optical system to be rotated left and right.
As described above, conventional CT scanners generally include an X-ray generator, a mechanism for rotating a subject, and a detector. The object is disposed between the X-ray generator and the detector, and X-rays are applied in a cross-sectional direction of the object at various positions. In X-ray CT scanners, attenuation of X-rays by different attenuation coefficient of substances is measured as data from different directions, and the data is converted into a cross-sectional image by mathematical operations using a computer. Thereby, the cross-sectional image corresponding to a scanned area of the subject is reconstructed and shown.
Further, these CT scanners are divided into medical and industrial CT scanners according to the kind of the subject, the observation area of the subject, and the purpose of scanning the subject.
The existing industrial X-ray CT scanners provide high-definition results, but they can measure only an object such as a disassembled part that can be placed on the turntable. For this reason, industrial X-ray CT scanners have the drawback of not being able to be used for, for instance, a pipe-line that is attached to a process system and thus is not able to be placed on the turntable.
Further, the existing image diagnostic apparatuses of the fan beam type, the collimated beam type, etc. having a stereotyped structure are next to impossible to move and use for undetachable process systems and their peripheral units.
That is, since the typical industrial X-ray CT scanners perform tomography scanning on a detachable object using a turntable, they cannot measure an undetachable object. There are many undetachable objects such as industrial process. The demand of tomography scanning for industrial process is increasing but conventional CTs cannot be applied for industrial process. It is preferable to provide a commercialized CT scanner that can be substantially applied to these objects. However, no CT scanner that meets all requirements has been provided up to now.